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      <title>2、url - 学习卡片</title>
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      <div class="header">
        <h1>2、url - 学习卡片</h1>
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    <div class="card-container" onclick="this.classList.toggle('flipped');">
      <div class="card">
        <div class="card-face card-front">
          <div class="card-category">理论</div>
          <div class="card-question">根据文档，什么是统一资源定位符（URL）？</div>
          <div class="card-footer">点击卡片查看答案</div>
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        <div class="card-face card-back">
          <div class="card-category">理论</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">统一资源定位符（Uniform Resource Locator）是一个指向互联网资源的指针。在Java中，它被封装为API，方便进行网络通信。</div>
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          <div class="card-source">来源: URL</div>
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          <div class="card-category">技术</div>
          <div class="card-question">一个标准的URL由哪些部分组成？请写出其格式。</div>
          <div class="card-footer">点击卡片查看答案</div>
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        <div class="card-face card-back">
          <div class="card-category">技术</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">一个标准的URL格式为：protocol :// hostname[:port] / path /[?query]。</div>
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          <div class="card-source">来源: URL</div>
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    <div class="card-container" onclick="this.classList.toggle('flipped');">
      <div class="card">
        <div class="card-face card-front">
          <div class="card-category">技术</div>
          <div class="card-question">在Java中，如何基于一个基础URL（baseURL）和一个相对URL（relativeURL）来构建一个新的URL对象？</div>
          <div class="card-footer">点击卡片查看答案</div>
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        <div class="card-face card-back">
          <div class="card-category">技术</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">可以通过构造函数 `URL(URL baseURL, String relativeURL)` 来创建。其中，baseURL代表绝对地址，relativeURL代表相对地址。</div>
          </div>
          <div class="card-source">来源: 1 URL的创建</div>
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    <div class="card-container" onclick="this.classList.toggle('flipped');">
      <div class="card">
        <div class="card-face card-front">
          <div class="card-category">理论</div>
          <div class="card-question">什么是HttpURLConnection？它与URLConnection有何关系？</div>
          <div class="card-footer">点击卡片查看答案</div>
        </div>
        <div class="card-face card-back">
          <div class="card-category">理论</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">HttpURLConnection是一个支持HTTP特定功能的URLConnection。它继承自URLConnection，可用于向指定网站发送GET和POST请求。</div>
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          <div class="card-source">来源: HttpURLConnection</div>
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    <div class="card-container" onclick="this.classList.toggle('flipped');">
      <div class="card">
        <div class="card-face card-front">
          <div class="card-category">机制</div>
          <div class="card-question">如何从一个URL对象获取其对应的URLConnection连接对象？</div>
          <div class="card-footer">点击卡片查看答案</div>
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        <div class="card-face card-back">
          <div class="card-category">机制</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">通过调用URL对象的 `openConnection()` 方法。该方法会返回一个URLConnection对象，它表示到URL所引用的远程对象的连接。</div>
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          <div class="card-source">来源: HttpURLConnection</div>
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        <div class="card-face card-front">
          <div class="card-category">模式</div>
          <div class="card-question">文档中提到了哪种使用内存流优化文件下载程序的方法？</div>
          <div class="card-footer">点击卡片查看答案</div>
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        <div class="card-face card-back">
          <div class="card-category">模式</div>
          <div class="card-answer-wrapper">
            <div class="card-answer">采用`ByteArrayOutputStream`先将数据写入到内存中，然后再一次性地将内存中的数据写入到目标文件中。</div>
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          <div class="card-source">来源: 5 案例二：采用内存流优化上述程序</div>
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